

So going back to the title, what to study? Maybe some specific book? Private classes/courses?
Networking. If you want to understand the reasoning behind things this is where you start. A good foundation in tcp/ip, the 7 layer network stack, as well as basic network protocols (dns, dhcp, http, etc.) will go a long way toward helping you troubleshoot when things go wrong.
Maybe throw in some operating systems study as well for when you start to use docker.


Terraform, ansible and kubernetes (microk8s).
K8s in particular has been a huge change to simplifying my network despite the complexities involved and the initial learning curve. Deploying and updating services is much easier now.